From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751920AbbJTGa3 (ORCPT ); Tue, 20 Oct 2015 02:30:29 -0400 Received: from mailgw02.mediatek.com ([218.249.47.111]:53251 "EHLO mailgw02.mediatek.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1750966AbbJTGa1 (ORCPT ); Tue, 20 Oct 2015 02:30:27 -0400 X-Listener-Flag: 11101 Message-ID: <1445322554.4858.12.camel@mhfsdcap03> Subject: Re: [PATCH v9 4/5] xhci: mediatek: support MTK xHCI host controller From: chunfeng yun To: Mathias Nyman CC: Mathias Nyman , Rob Herring , Mark Rutland , Matthias Brugger , Felipe Balbi , Sascha Hauer , , , , "Roger Quadros" , , , John Crispin , Daniel Kurtz , Sergei Shtylyov , Kishon Vijay Abraham I , Pawel Moll , Ian Campbell , Kumar Gala , "Greg Kroah-Hartman" Date: Tue, 20 Oct 2015 14:29:14 +0800 In-Reply-To: <5624D33D.5090807@intel.com> References: <1443495698-32233-1-git-send-email-chunfeng.yun@mediatek.com> <1443495698-32233-5-git-send-email-chunfeng.yun@mediatek.com> <561FBC40.7020100@linux.intel.com> <1445131519.17024.10.camel@mhfsdcap03> <5624D33D.5090807@intel.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3-0ubuntu6 Content-Transfer-Encoding: 7bit MIME-Version: 1.0 X-MTK: N Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org hi, On Mon, 2015-10-19 at 14:25 +0300, Mathias Nyman wrote: > >> > >> So basically we are trying to use as many microframes as possible with as few packets > >> per microframe as possible. > >> > >> Did I understand this correctly? > > Yes, you are right. > > > >> How will devices react if they expect to get 16 packets every 16th microframe, > >> but they get one packet every microframe instead? > > I think that the synchronous endpoint must specify its period by > > bInterval, but can't specify how data should be transfered during the > > period by the host, and it just only receives data passively. So the > > device can receive data correctly in the case(bInterval is 5). > > > > quote from usb3_r1.0 section4.4.8 Isochronous Transfers: > > "The host can request data from the device or send data to the device at > > any time during the service interval for a particular endpoint on that > > device" > > > > As I understand the 4.4.8 section it just means the device can't assume a fixed > time interval between transfers, meaning that the host can use the last microframe > in one esit and the first microframe in the next esit, but still only use 1 microframe > per esit. > > Section 8.12.6.1 describes how a 11 packet isoc transfer is allowed to be split > to 1 burst of 11 packets, 2 burst (8 + 3), 3 burst (4+4+3) 6 bursts (2+2+2+2+2+1) or > 11 bursts of 1. These are however all within the same microframe. Splitting the > transfer into several microframes in a esit kind of makes the whole interval concept pointless. > It doesn't say that the packets should be transfered within the same microframe (bus interval), as I understand it means service interval; The direct prove resides in figure 8-56/8-57. Term: 1. BI, bus interval, a 125 us period that establishes the internal boundary of service interval, aka uframe; 2. SSI, Support Smart Isochronous; 3. DBI, Data in this Bus Interval is done; 4. NBI, Numbers of Bus Interval; As the figure shows, the service interval = 8 BI, that host distribute 2 packets @1st uframe, keep U1/U2 state for the next 3uframe, then transmit 4 packets @4th uframe, and the remaining 3 packet in the last frame. Please notice that this just is an example illustrated by spec, but we can derive the conclusion that the distribution of packet in a service interval is completely decided by host, and can split isoc transfers across multiple uframes. PS: as you can see, MTK implementation of schedule algorithms is an implementation of Smart Isochronous of which the smart side resides in software. > -Mathias > > > > >